Methods and apparatus for array based lidar systems with reduced interference

ABSTRACT

An array-based light detection and ranging (LiDAR) unit includes an array of emitter/detector sets configured to cover a field of view for the unit. Each emitter/detector set emits and receives light energy on a specific coincident axis unique for that emitter/detector set. A control system coupled to the array of emitter/detector sets controls initiation of light energy from each emitter and processes time of flight information for light energy received on the coincident axis by the corresponding detector for the emitter/detector set. The time of flight information provides imaging information corresponding to the field of view. Interference among light energy is reduced with respect to detectors in the LiDAR unit not corresponding to the specific coincident axis, and with respect to other LiDAR units and ambient sources of light energy. In one embodiment, multiple array-based LiDAR units are used as part of a control system for an autonomous vehicle.

FIELD OF THE INVENTION

The invention relates generally to determining presence and position ina surrounding space of objects that interact with propagatingelectromagnetic waves. More particularly, the present invention relatesto non-scanning LiDAR systems using an array of emitter/detector sets tocover a given field of view that provides for reduced interference dueto crosstalk among emitters within a given LiDAR unit and also amongdifferent LiDAR units.

BACKGROUND OF THE INVENTION

LiDAR (light detection and ranging) uses laser technology to makeprecise distance measurements over short or long distances. LiDAR unitshave found widespread application in both industry and the researchcommunity.

The predecessor technology to current LiDAR units were object detectionsystems that could sense the presence or absence of objects within thefield of view of one or more light beams based on phase shift analysisof the reflect light beam. Examples of these kinds of object detectionsystems in the field of vehicle “blind spot” warning systems includeU.S. Pat. Nos. 5,122,796, 5,418,359, 5,831,551, 6,150,956, and6,377,167.

Current LiDAR units are typically scanning-type units that emit beams oflight in rapid succession, scanning across the angular range of the unitin a fan-like pattern. Using a time of flight calculation applied to anyreflections received, instead of just a phase shift analysis, the LiDARunit can obtain range measurements and intensity values along thesingular angular dimension of the scanned beam. LiDAR units typicallycreate the scanning beam by reflecting a pulsed source of laser lightfrom a rotating mirror. The mirror also reflects any incomingreflections to the receiving optics and detector(s).

Single-axis-scan LiDAR units will typically use a polygonal mirror and apulsed laser source to emit a sequence of light pulses at varying anglesthroughout the linear field of view. Return signals are measured by abandpass photoreceptor that detects the wavelength of light emitted bythe laser. The field of view of the photoreceptor covers the entireone-dimensional scan area of the laser. Thus, each subsequent emittedpulse of laser light must occur only after the reflected signal has beenreceived for the previous laser pulse. Dual-axis-scan LiDAR unitsproduce distance-measured points in two dimensions by using, forinstance, a pair of polygonal mirrors. The horizontal scan mirrorrotates at a faster rate than the vertical scan mirror.

Flash LiDAR devices like those disclosed in U.S. Pat. No. 8,072,581offer a way to acquire a 3D map of a scene via a solid state or mostlysolid state approach. These devices illuminate an entire 2D field ofview with a blanket of light and measure the return value time for eachphotoreceptor location in the field of view. These approaches arerelegated to very close proximity applications due to the low incidentlaser power for each location in the field of view. For flash LiDAR atlonger ranges, the usable field of view is typically too small forapplications like autonomous vehicle navigation without the use of highperformance cameras operating in the picosecond range for exposuretimes.

U.S. Pat. No. 7,969,558 describes a LiDAR device that uses multiplelasers and a 360-degree scan to create a 360-degree 3D point cloud foruse in vehicle navigation. The disclosed system has two limitations.First, the rotating scan head makes the unit impractical for widespreaduse on autonomous vehicles and makes it unusable for inclusion in mobiledevices like smart phones, wearable devices, smart glasses, etc. Second,multiple units cannot work effectively in the same relative physicalspace due to the potential of crosstalk.

Scanning LiDAR units typically utilize a single laser, or multiplelasers, all operating at the same wavelength. Care must be taken toensure that signals received by the photoreceptor are reflected lightfrom the desired emitted source. Two LiDAR units, call them A and B,operating with lasers at the same wavelength have the potential toexperience crosstalk. Inbound signals at the A detector wavelength of,for example, 650 nm could be a reflected signal from an emitter for unitA, a reflected signal from unit B, or a signal directly from an emitterof unit B. In an application like autonomous vehicle navigation withmultiple LiDAR sensors per vehicle on a busy roadway, the potential forcrosstalk among pulsed-laser LiDAR units is quite high. Crosstalkinterference between individual LiDAR units can be reduced by utilizingtime division synchronization between the units wherein the transmittimes of one unit do not overlap with the transmit times of other units.This synchronization of individual units will lower the capture rate foreach device and is impractical when the individual units are integratedwith separate, independently-controlled systems.

The error mode for crosstalk interference among LiDAR units willtypically be one or more distances being computed as lower than theactual distances or failure to find a signal, resulting in no valuebeing reported for an individual point. For LiDAR units that utilizesignal intensity from the target information, the recording intensitywill typically be higher than the actual intensity of the returnedsignal.

U.S. Pat. No. 8,363,511 attempts to overcome the crosstalk interferenceproblem in short range object detection systems by emitting anddetecting a series of encoded pulses as part of the ultrasonic ormicrowave waves generated by the transducers. While this kind ofencoding technique has the potential to reduce some occurrences ofcrosstalk interference, encoding techniques are still not sufficient forapplications that may encounter an unknown and large numbers of devicesthat are simultaneously operating at the same or similar wavelength ofemitter energy.

U.S. Pat. No. 7,830,532 also attempts to address the crosstalkinterference problem in the context of short range object detectionsystems using infrared light for fixed location units such as garagedoor sensor detectors by various combinations of time division,frequency division, encoding and testing modes. While these kinds ofsolutions might work in the context of limited numbers of fixed objectdetection systems, they are not practical or effective in the context ofcurrent LiDAR technologies, especially when used in moving environments.

LiDAR units have the potential to be utilized extensively inapplications like autonomous vehicle navigation, mobile computing andwearable devices. However, problems remain in developing effective LiDARunits that can address the interference challenges and operate reliablyin an environment where hundreds or thousands of like devices areoperating simultaneously.

SUMMARY OF THE INVENTION

LiDAR (light detection and ranging) systems in accordance with variousembodiments of the invention use an array of emitter/detector sets tocover a given field of view where each emitter/detector set isconfigured to receive reflected light energy that is on a givencoincident axis unique for that emitter/detector set and process time offlight information for that received light energy. The combination of anarray of emitter/detector sets coupled with the on-coincident axisapproach for each of the emitter/detector sets provides for reducedinterference among emitters within a given LiDAR unit and also amongdifferent LiDAR units.

LiDAR systems in accordance with various embodiments of the inventionmay use a multi-bit sequence of emitter pulses for each emitter/detectorcycle. The multi-bit sequence is locally unique to each emitter, whereinthe bit sequence differs from the bit sequences for emitters whosecoincident axis/vectors are in close proximity. By selecting locallyunique bit patterns for each emitter, the interference from otheremitters and other similar LiDAR devices is dramatically reduced. Theuse of multi-bit emitter sequences also results in reduced interferencefrom non-LiDAR devices that are transmitting or reflecting energy at thetarget detector wavelength.

In various embodiments, the array comprises a non-scanning, solid-statedevice having a multitude of emitter/detector sets arranged on agenerally planer surface. In some embodiments, each emitter/detector setis a single pair of an emitter and a detector. In other embodiments, asingle emitter can be optically configured to provide on-coincident axislight energy to multiple different detectors, with each uniqueon-coincident axis combination of the single emitter and a differentdetector comprising a different emitter/detector set. In someembodiments, the number of emitter/detector sets can range from a 16×16array of emitter/detector sets up to an array of 4096×4096emitter/detector sets. In other embodiments, the number ofemitter/detector sets and the configuration arrangement can be more orless, and can be planar or non-planar depending upon the specificapplication for which the LiDAR system is designed.

In various embodiments, a pulse generation controller is configured totransmit a sequence of pulses from each of the emitters and a controlunit is configured to compute a time of flight measurement for radiationreceived at each of the corresponding on-coincident axis detectors. Thecontrol unit that is coupled to the detector output can be a softwareprocessing unit or a hardware circuitry for analyzing the light energyin order to extract information about objects within the field of viewof the array-based LiDAR unit. In some embodiments, the output of thedetector is coupled to a microprocessor unit (MPU) that is programmed toperform the analysis on the received light energy. In other embodiments,a pulse detection circuit is configured to analyze an output signal ofthe detector, such as an associated output signal of a detector shiftregister. While the timing of the sequence pulses is known within theLiDAR unit, coorindation and advance knowledge of the timing and/orwavelength of emitted light energy from other LiDAR units is notrequired as in prior art LiDAR systems in order to reduce crosstalk andinterference among different LiDAR units.

In various embodiments, the field of view of the LiDAR unit ispredetermined based on the optic configuration associated with each ofthe sets of emitter/detectors for a unique on-coincident axis. In oneembodiment, each emitter/detector set includes an optical waveguidethrough which the received light energy is directed for theon-coincident axis for that emitter/detector set. In another embodiment,each emitter/detector set in an array of emitter/detector sets includesa micro-lens through which the emitted light energy is directed for theon-coincident axis for that emitter/detector set. In some embodiments,an array of micro-lens optics includes a micro-lens unique for eachemitter/detector set. In other embodiments, an array of micro-lensoptics includes more than one micro-lens for each emitter. In otherembodiments, a macro lens arrangement can be used to establish theunique on-coincident axis associated with each emitter/detector set. Insome embodiments, such as the micro-lens array embodiment, the macrofield of view of the LiDAR unit is effectively established uponfabrication of the micro-lens array together with the array ofemitter/detector sets. In other embodiments, the macro field of view maybe changed by a global lensing arrangement that is adjustable.

In various embodiments, each detector in the array-based LiDAR unit hasa unique angle of coincidence relative to the optic configurationthrough which the reflected light energy is received. For purposes ofthe present invention, the angle of coincidence of a given detector isdefined as the center of the area of the light beam received by thedetector not including any modifications to the light beam due to opticelements internal to the LiDAR unit. In some embodiments, the lightenergy is emitted and received as collimated or coherent electromagneticenergy, such as common laser wavelengths of 650 nm, 905 nm or 1550 nm.In some embodiments, the light energy can be in the wavelength ranges ofultraviolet (UV)—100-400 nm, visible—400-700 nm, near infrared(NIR)—700-1400 nm, infrared (IR)—1400-8000 nm, long-wavelength IR(LWIR)—8 um-15 um, or far IR (FIR)—15 um-1000 um. The variousembodiments of the present invention can provide reduction ofinterference at these various wavelengths not only among emitted andreflected light energy of LiDAR devices, but also emitted and reflectedlight energy from other ambient sources such as vehicle headlights andthe sun that will also be sources of interference for typical LiDARunits.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a single-axis-scan device according to the prior art.

FIG. 2 illustrates a dual-axis-scan device according to the prior art.

FIG. 3 illustrates a functional block diagram of a measurement systemaccording to an embodiment.

FIG. 4 illustrates the geometry of multiple emitters according to anembodiment.

FIGS. 5a and 5b illustrate the functional layers of a vertical emitterwith a micro lens according to an embodiment.

FIG. 6 illustrates the functional layers of vertical emitters with adevice emitter lens according to an embodiment.

FIG. 7 illustrates the beam profiles for emitted light according to anembodiment.

FIG. 8 illustrates the geometry of receptors with directional waveguidesaccording to an embodiment.

FIG. 9 illustrates the functional layers of a receptor with adirectional waveguide according to an embodiment.

FIG. 10 illustrates the functional layers multiple receptors with adevice detector lens according to an embodiment.

FIGS. 11a and 11b illustrates two device layout options according to anembodiment.

FIG. 12 illustrates a pulse timing sequence for multiple emittersaccording to an embodiment.

FIG. 13 illustrates the timing of a detector signal and how it iscompared to the emitted pulse sequence according to an embodiment.

FIG. 14 illustrates the functional block diagram for the emitter anddetector circuitry according to an embodiment.

FIG. 15 illustrates the emitter and detector timing for one measurementsequence according to an embodiment.

FIG. 16 illustrates the functional block diagram for the emitter anddetector circuitry for target intensity measurements according to anembodiment.

FIG. 17 illustrates the functional block diagram for the detectorcircuitry for MPU detector processing.

FIGS. 18a and 18b illustrate a pattern utilized for emitted ray angleadjustments according to an embodiment.

FIG. 19 illustrates a dense detector array according to an embodiment.

FIG. 20 illustrates an orthogonal dense detector array according to anembodiment.

FIG. 21 illustrates the operational flowchart of the device according toan embodiment.

FIG. 22 illustrates the use of the device in a vehicle navigationapplication.

FIG. 23 illustrates the use of the devices in an airborne dataacquisition application.

DETAILED DESCRIPTION OF THE DRAWINGS

Single-axis-scan LiDAR (light detection and ranging) units willtypically use a polygonal mirror and a pulsed laser source to emit asequence of light pulses at varying angles throughout the linear fieldof view. Return signals are measured by a bandpass photoreceptor thatdetects the wavelength of light emitted by the laser. The field of viewof the photoreceptor covers the entire scan area of the laser. Thus,each subsequent emitted pulse of laser light must occur only after thereflected signal has been received for the previous laser pulse. FIG. 1shows some essential elements of a typical single-axis-scan LiDAR unit.The laser source is pulsed multiple times as each face of the polygonalmirror rotates past the laser axis. Each rotation of a mirror facecorresponds to a single linear scan of locations. For each point of ascan, the distance and angle are recorded. Many LiDAR applications alsoinclude return signal intensity, thus encoding more information aboutthe object that produced the reflected the return signal. Twodimensional scans of objects and/or scenes are created by affixing asingle-axis-scan LiDAR to an object in motion, with the scan axis of theLiDAR roughly perpendicular to the travel direction of the vehicle.

Dual-axis-scan LiDAR units produce distance-measured points in twodimensions by using, for instance, a pair of polygonal mirrors. Thehorizontal scan mirror rotates at a faster rate than the vertical scanmirror. FIG. 2 shows some of the essential elements of a typicaldual-axis scan LiDAR unit. Other methods can be used to achieve laserscans in two dimensions. These methods, for the most part, rely onmechanical or electromagnetic movement of one or more objects to achievethe laser scan in two dimensions.

LiDAR units will utilize a single laser, or will utilize multiple lasersall operating at the same wavelength. Care must be taken to ensure thatsignals received by the photoreceptor are reflected light from thedesired emitted source. Two LiDAR units, call them A and B, operatingwith lasers at the same wavelength have the potential to experiencecrosstalk. Inbound signals at the A detector wavelength of, for example,650 nm could be a reflected signal from an emitter for unit A, areflected signal from unit B, or a signal directly from an emitter ofunit B. In an application like autonomous vehicle navigation withmultiple LiDAR sensors per vehicle on a busy roadway, the potential forcrosstalk interference among pulsed-laser LiDAR units is quite high.Crosstalk interference between individual units can be reduced byutilizing synchronization between the devices wherein the transmit timesof one device do not overlap with the transmit times of other devices.This synchronization of individual units will lower the capture rate foreach device and is impractical when the individual devices areintegrated with separate, independently-controlled systems.

Referring to FIG. 3, a block diagram of an optoelectronic LiDAR devicein accordance with an embodiment is depicted. According to anembodiment, optoelectronic LiDAR device 300 can comprise anemitter/detector array 10, a pulse generation circuit 22, a samplingcircuit 12 and a control unit 20. Emitter/detector array 10 can comprisea plurality of emitter elements 100 and detector elements 200symmetrically arranged in rows and columns. Each emitter of emitterelements 100 of emitter/detector array 10 can comprisevertically-constructed laser diodes that can be configured to projectbeams of light at known angles relative to a vector of the device normalto a plane of the array 10. Detector elements 200 of emitter/detectorarray 10 can comprise a bandpass photodetector that can be configured togenerate waveguides at known angles relative to a vector of the devicenormal to a plane of the array 10. For each emitter/detector set ofelements 100/200, the emitter and detector vectors are coincident andform a common on-coincident axis that is at an angle relative to avector normal to the plane of the array that is unique for thatemitter/detector set.

For purposes of the present invention, the terminology “on-coincidentaxis” will be used to refer to the common known angle of both theemitted and reflected electromagnetic energy for a given set ofemitter/detector elements. It will be understood that “on-coincidentaxis” includes energy emitted or reflected on the specific vectors thatdefine the coincident axis, as well as energy emitted or reflected atangles that are relatively close to the same angle, such as angleswithin the surface area of the received light beam as defined by theedges of the light beam entering the LiDAR unit that will be received atthe detector.

In embodiments, pulse generation circuit 22 can comprise a series oflogic devices such as a sequence of shift registers configured togenerate an output signal, such as pulse, to activate an emitter ofemitter elements 100. Pulse generation circuit 22 utilizes at least onefirst clock signal generated by a timer 24 to initiate the propagationof data through each of the sequence of shift registers. In someembodiments, each individual emitter of emitter elements 100 has adedicated shift register in the pulse generation circuit 22. In otherembodiments, unique control signals, multiplexed control signals orcontrol signals received over a parallel or serial bus connection may beused to initiate the propagation of the emitter elements.

In an embodiment, sampling circuit 12 can comprise an analog-to-digitalconverter and/or other electronic components such as transistors orcapacitors to process an output signal from each of the plurality ofdetector elements 200. Each detector of detector elements 200 can beconfigured as a photoreceptor such as a photodiode or phototransistorwhich converts light into an electrical signal. The electrical signal isthen converted to a discrete-time digital signal (i.e., sampled) bysampling circuit 12, whereby the sampled digital signals are accumulated(i.e., summed or averaged) and stored by detector shift register 14 orother type of digital memory element. Detector shift register 14 canutilize a second clock signal generated by timer 24 to triggeraccumulation of the digital signals based on an oscillation event of thesecond clock signal. In embodiments, the frequency of the second clocksignal generated by timer 24 for detector shift register 14 should begreater than twice the frequency of the first clock signal generated bytimer 24 for the pulse generation circuit 22:

f _(detector)>2*f _(emitter)

where f_(detector)=the frequency of the detector shift register clock;and

-   -   f_(emitter)=the frequency of the pulse generation circuit clock.        In operation, for example, the detector frequency will be eight        to 32 times the emitter frequency when hardware detection is        used, and will be eight to 128 times the emitter frequency when        software detection is used.

In other embodiments, optoelectronic device 300 can further comprise apulse detection unit 16 that can be configured to analyze the outputsignal of pulse generation circuit 22 in comparison to the output signalof detector shift register 14 to identify a match between the outputsignals. Pulse detection unit 16 utilizes a third clock signal generatedby timer 24 to determine a time at which a match in the output signalsis detected. In embodiments, pulse detection unit 16 can comprisecomputer readable media (not shown) such as RAM, ROM, or other storagedevices to store the time at which a match was detected for eachdetector of detector elements 200. At the end of a sampling sequence thecontrol unit 20 will read the match time for each detector of detectorelements 200 and compute the distance to the reflected object based on atime of flight calculation. The distance for each emitter of emitterelements 100 and detector of detector elements 200 is stored in an imagememory 18. Each emitter of emitter elements 100 has a vector associatedwith it that corresponds to the axis of the beam from the emitter ofemitter elements 100 relative to the normal vector of the device. Allemitter element 100 vectors are stored in a vector memory 26. Allinformation is transferred to/from the device via the input/output (I/O)28 connection.

Referring to FIG. 4, an illustration of a perspective view of emitterunit 102 according to an embodiment is shown. In embodiments, emitterunit 102 can comprise emitter elements 100 arranged symmetrically abouta top surface of emitter unit 102. Each emitter of emitter elements 100is configured to emit a beam of light 110. The normal vector is shown asthe z-axis 134 in the right-hand-rule coordinate system. The field ofview may vary with each optoelectronic device depending upon theapplication. A long range device, for example, will have a narrow fieldof view for both the horizontal and vertical dimensions. The maximumhorizontal field of view for a flat device, measured in alignment withan x-axis 130, is 180 degrees, and the maximum vertical field of viewfor a flat device, measured in alignment with a y-axis 132, is 180degrees. Fields of view greater than 180 degrees along both the x-axisand y-axis are achievable by utilizing 3D semiconductor fabricationtechniques or by including additional optics that allow a flatsemiconductor device to project incident radiation into the negativez-axis space.

For a device where the angular spacing of successive emitter elements100 is equivalent across the horizontal and vertical fields of view,each emitter of emitter elements 100 projection angle beam of light 110is expressed as a emitter vector 120 utilizing uvw nomenclature, where ucorresponds to the x-axis 130, v corresponds to the y-axis 132, and wcorresponds to a z-axis 134:

uvw_(ij)=[tan(FOV_(horiz)*(½−m/(M−1))),tan(FOV_(vert)*(½−n/(N−1))),1]  (eq.2)

where FOV_(horiz) is the horizontal field of view expressed in degrees

-   -   FOV_(vert) is the vertical field of view expressed in degrees    -   M is the number of horizontal elements in the emitter array    -   m signifies the horizontal element number, ranging from 0 to M−1    -   N is the number of vertical elements in the emitter array    -   n signifies the vertical element number, ranging from 0 to N−1        Various other methods are available for the selection of emitter        vector 120 for emitter elements 100. Some device applications        may require a higher point density at or near the center of the        field of view and a sparser distribution of points toward the        edges of the field of view.

Referring to FIG. 5a a cross section of a side view of an emitter ofemitter elements 100 fabricated with a semiconductor laser is shownaccording to an embodiment. In embodiments, emitter elements 100 can befabricated to emit a light beam in the direction of the semiconductorlayer stack. Utilizing a vertical transmission layer stack allows forsmall spacing between individual emitters on a device and allows forsimpler optics.

The semiconductor laser comprises a substrate 50, a lower reflector 52,an active layer 54, a high-resistance region 56, an upper reflector 58and an electrode 60 which are sequentially stacked on the substrate 50.In an embodiment, each of the lower reflector 52 and the upper reflector58 is a distributed Bragg reflector which is formed by alternatelystacking material layers having different refractive indexes and havingopposite doping type.

The light emitted from a vertical semiconductor laser will be adiverging beam. An emitter lens 66 is fabricated on the top of the laserstack to create a collimated beam of light 68. A directional lens 70directs the collimated beam of light 68 along a desired emitter vector120.

For high-precision applications emitter vector 120 of each emitter ofemitter elements 100 may require minute adjustments. In embodiments,emitter elements 100 can comprise directional lens electrodes 62, 64 toprovide a voltage differential laterally across the directional lens 70.In a preferred embodiment each directional lens 70 will have anelectrode pair in both the x-axis and y-axis, with each electrode paircontrolling emitter vector 120 along the x-axis and y-axis. Thedirectional lens electrodes 62, 64 values are addressable and aremodified by the control unit 20.

One skilled in the art will understand that alternate constructions ofmicro-lenses are possible. In accordance with various embodiments of theinvention, such alternate constructions should result inindependently-controlled emitters that produce beams at known orcharacterizable vectors 120 relative to the device's normal vector 134.Constructions for adjustable emitter micro lenses can include, but arenot limited to, electro-optic materials that change refractive index inresponse to an electric field, piezoelectric materials that experience amodification of their shape in response to an electric field, ortransparent encapsulated liquid lenses. FIG. 5b shows the same verticalsemiconductor laser as FIG. 5a , with the exception of the emitter lens66. The dual directional lens 70 in FIG. 5b has two distincttransmission surfaces. Roughly 50% of the collimated beam of light 68 isdirected along emitter vector 120, while most of the remaining lightfrom beam of light 68 is directed along vector 121. Since both beams arecreated from the same emitter of emitter elements 100, they will havethe same transmitted pulse waveform. Each reflected beam, however, willhave a different coincident axis and will be detected by a separatewaveguide detector or by a separate detector or group of detectors inthe dense detector array. In an embodiment, the number of distincttransmission surfaces on a multi-directional lens can vary from two to64 provided the coincident axis of each unique surface is sufficientlydifferent from the coincident axis of the other lens surfaces.

Referring to FIG. 6, a cross section side view of emitter elements 100with a macro lens 80 according to an embodiment is shown. Inembodiments, each emitter of emitter elements 100 and emitter lens 66produces a converging beam 84. The macro lens 80 is configured todiverge to produce a plurality of beams 82 along a multitude of emittervectors (coincident axes) 120 throughout the device's field of view.

Emitter directional lens electrodes 86, 88 may be added to provide avoltage differential laterally across the macro lens 80. In anembodiment, the macro lens 80 will have an electrode pair in both thex-axis and y-axis, with each electrode pair controlling emitter vector(coincident axis) 120 along the x-axis and y-axis. The emitterdirectional lens electrodes 86, 88 values are addressable and aremodified by the control unit 20.

Referring to FIG. 7, a beam profile for multiple emitters according toan embodiment is shown. The top diagram shows a perfectly collimatedbeam 92 that produces a round spot 94 on the surface of the reflectingobject. The beam intensity is uniform throughout the round spot 94, andthe intensity of the light transitions sharply at the edge of the roundspot 94. In precision LiDAR systems, a beam such as collimated beam 92has advantages. First, a smaller round spot 94 size will result in fewerlocations within the device field of view being illuminated. Since thegoal of LiDAR is to measure the distance to a point at a knowncoincident angle, reducing the number of points that generate a returnsignal will increase the device's precision. Second, a smaller roundspot 94 will generally reduce or remove crosstalk with detectors thatare near the on-coincident axis matched detector for this emitter 90.The bottom diagram in FIG. 7 shows a more typical beam profile. The beam96 diverges as it travels through space. The spot 98 on the surface ofthe reflected object is elliptical in shape. The light intensity isnon-uniform throughout the surface of the spot 98. Depending on emitterconstruction, the spot will typically have a two-dimensional Gaussianprofile or a second-order profile. The point of greatest intensity willnot always be the center point of the spot 98.

Referring to FIG. 8, a top view of detector elements 200 geometry on theemitter/detector array 10 surface is shown according to an embodiment.Light 210 is received at each detector of detector elements 200. Eachdetector of detector elements 200 has an optimal receive detector vector(coincident axis) 220 along which the maximum optical energy will betransferred. Inbound optical energy that is slightly non-parallel to thedetector vector 220 will be partially reduced in intensity due towaveguide blocking or due to the macro lens. Inbound optical energy thatis more than slightly-non-parallel to the receive detector vector(coincident axis) 220 will be substantially blocked by the detectorwaveguide or directed elsewhere by the macro lens. For purposes of thepresent invention, the coincidence axis of a given detector is definedas the center of the area of the light beam 210 as received by thedetector not including any modifications to the light beam due to opticelements internal to the LiDAR unit.

Referring to FIG. 9, a cross section of a side view of a detector ofdetector elements 200 element fabricated with an angular waveguide isshown according to an embodiment. The detector of detector elements 200is fabricated to receive light transmitted substantially opposite to thedirection detector vector 220 of the waveguide axis. The waveguidedetector comprises a substrate 50, a photoreceptor 224, a bandpassfilter layer 226, a protective layer 228 and the waveguide material 215.A waveguide 222 shall be an air gap or shall consist of a material thatis substantially transparent to the wavelength of emitted light. Thewaveguide wall shall consist of a material that is substantiallynon-reflective for the wavelength or range of wavelengths of the emittedlight. The waveguide 222 geometry is a slightly-diverging trapezoidalcone. The amount of divergence will depend on the minimum range of thedevice, the lateral distance on the device between the detector vector220 and the axis of its associated emitter of emitter elements 100, andthe depth of the waveguide.

Referring to FIG. 10 a cross section side view of a detector elementwith a macro detector lens 230 is shown according to an embodiment. Inembodiments, detector elements 200 comprise a substrate 50, aphotoreceptor 224, a bandpass filter layer 226 and a protective layer228. In other embodiments, light can be received from a diverging fieldof view at a macro detector lens 230 that directs in-bound light to thesurface of detector elements 200.

In embodiments, macro detector lens 230 comprises detector directionallens electrodes 232, 234 positioned on the x-axis and y-axis, wherebythe electrodes 232, 234 are configured to control a detector vector 220along the x-axis and y-axis. The directional lens electrodes can beconfigured to provide a voltage differential laterally across macrodetector lens 230. The directional lens electrode 232, 234 values areaddressable and are modified by the control unit 20.

Referring to FIG. 11a , a physical device layout according to anembodiment is shown. In an embodiment, emitter elements 100 and detectorelements 200 can be symmetrically arranged in an electro-optical section242 of the device 240. The number of emitter elements 100 can be equalto the number of detector elements 200, and each detector of detectorelements 200 is “paired” with a designated emitter of emitter elements100. The pulse sequence transmitted by an emitter of emitter elements100 will be sensed and detected only by its paired detector of detectorelements 200. In embodiments, a single global lens can be utilized forboth emitter elements 100 and detector elements 200. When single globallens are used for emitter elements 100 and detector elements 200 optics,the distance between the emitter/detector pair must be minimal. In otherembodiments, for example, where micro lens are used for emitter elements100, the distance between each emitter/detector is not as important andcan vary according to embodiments. Larger distances between micro-lensemitter elements and waveguide detector elements will require slightlylarger diverging waveguides according to FIG. 9. Device circuitry islocated in an electronic section 244 of the device 240.

Referring to FIG. 11b a physical device layout according to anembodiment is shown. In embodiments, emitter elements 100 can bearranged in an emitter electro-optical section 248 and detector elements200 can be arranged in a detector electro-optical section 246 of device240. The number of detector elements 200 can be equal to or greater thanthe number of emitter elements 100. In embodiments, for example, eachemitter/detector array will comprise K detector elements 200 for eachemitter of emitter elements 100, where K is an integer value from 1 to25.

In other embodiments, each waveguide detector of detector elements 200is “paired” with a designated emitter of emitter elements 100, wherebythe pulse sequence transmitted by an emitter of emitter elements 100will be sensed and detected only by its paired detector of detectorelements 200. For global lens detectors the number of detector elements200 will be typically 7 to 25 times the number of emitter elements 100,and the paired detector of detector elements 200 that corresponds toeach emitter of emitter elements 100 will be determined during device240 characterization. For embodiments that utilize waveguide detectors,the larger distances between emitter elements 100 and detector elements200 will require slightly larger diverging waveguides according to eq.3. Device circuitry is located in the electronic section 244 of thedevice 240.

Electronic section 242 and electro-optical sections 242, 246, 248sections for device 240 in FIGS. 11a and 11b can be implemented on thesame semiconductor die or on separate die that are placed together andinterconnected on a common substrate with common packaging.

FIG. 12 illustrates a timing sequence for multiple emitters. A highlevel 250 indicates the emitter is energized or turned on by the emittercontrol circuitry. The energizing level is shown for six emitters thathave coincident axes similar to one-another. The bit sequences utilize arotating primes pulse train and 38-bit sequences, and the emitter levelsare shown for a time period 252 ranging from 0 through 37. Since thevectors are similar, emitted energy from one emitter will possibly bereceived at a detector that is not its pair. To accommodate detection ofpulse sequences from a detector's paired emitter the pulse sequencesshown in FIG. 12 are sparsely populated. The circuitry for each paireddetector is configured to detect the pulse sequence from its pairedemitter.

Various methods exist for the selection and detection of pulse sequencesthat are locally distinct or differentiable and detectable relative toeach detector's spatial neighbors. Bit encoding schemes that can beutilized include but are not limited to unordered list of primes, randomnumbers, pseudo-random numbers, random sequences and pseudo-randomsequences. Bit generation schemes can include any encoding scheme whichproduces non-repeating, distinct values. Potential bit encryptionschemes include but are not limited to one time pad, Hash, DES, MD5, andAES. One skilled in the art can select the bit encoding or bitencryption scheme that best fits the computational power of the deviceand the non-repetitiveness requirements.

FIG. 13 illustrates a detector input signal 260 received by a detectorof detector elements 200 in response to an emitter pulse sequence 264.The detector input signal 260 will increase according to reflected lightemitted from emitter m, n and reflected off an object. The detectorcircuitry and the control unit will determine the distance of the objectthat reflected the signal by measuring the time of flight of the photonsin the emitter pulse sequence 264.

The detector input signal 260 will be sampled at a frequency inaccordance with eq. 1. In practice the sampling frequency will beconsiderably greater and will be a multiple of the emitter pulsefrequency. In FIG. 13 the sampling frequency for detector m, n is fourtimes the emitter frequency and the sampling times 266 are shown for t₀through t₆₁.

Each detector has a dedicated shift register into which the sampleddetector states are stored. A “one” is stored for each sampling timewhere the detector voltage is greater than a threshold value 262. Ateach sampling times 266 the bits in the shift register are transferredone location to the left according to the shift direction 284. Thecontrol unit clears all shift registers prior to the start of theemitter pulse sequence 264. The initial state of the shift register att₀ 268 is shown with all bits being set to zero. At t₀—when the emitterpulse sequence is initiated—the pulse compare circuitry will beginlooking for a “match” between the emitter pulse sequence 264 and thesampled sequence. The values transmitted in the emitter pulse sequence264 are stored by the control unit in the detector compare register 286for use by the compare circuitry.

The compare circuitry performs a comparison at every sampling time.After eleven sampling periods the shift register at t₁₁ 270 containssampled values from the first portion of the received waveform. At t₇₆the compare circuitry detects a match 274 for emitter bit 0, bit 7 andbit nine, but does not detect a match 276 for bit 4. Therefore, thesampled waveform does not correspond to the emitted waveform. At t₉₀ thecompare circuitry detects a match 280 at bit 0, bit 7 and bit 9 as wellas a match 282 at bit 4. Since all of the “ones” from a compare register272 have a corresponding match in the detector shift register 278, thecompare circuitry will flag and record the time at which the matchoccurred.

FIG. 14 illustrates functional blocks used for sending a bit sequence toan emitter of emitter elements 100 and processing the sensed signal froman associated detector of detector elements 200. The timer 24 producessynchronized clocks—an emitter clock that controls the timing of thepulses in the pulse generation circuit 22 and a detector clock thatgoverns the processing of information throughout the detectionfunctional blocks. The frequency of the detector clock will typically bean integer multiple of the emitter clock. The integer multiple for thedetector clock will depend on the bit sequence encoding scheme.

The output bit of the pulse generation circuit 22 produces the voltagelevel that will drive an individual emitter of emitter elements 100.Once the emitter sequence has started, the detector circuitry beginscollecting information from the detector of detector elements 200. Thesampling circuit 12 produces a multi-bit value that is continuouslycompared to the value in the threshold register 30. For sampled valuesgreater than the value in the threshold register 30, a threshold comparecircuitry 32 produces a true value or “1” in a positive logic system.The output of the threshold compare circuitry 32 is the input value forthe detector shift register 14. A new value is shifted into the detectorshift register 14 on each transition of the detector clock. The detectorcounter 36 is set to zero at the start of the emitter pulse sequence andwill increment its count on each detector clock pulse.

The detector compare register 35 contains the multi-bit value for theemitter pulse sequence. This register is typically a copy of the initialvalue loaded into the pulse generation circuit 22. A sequence detectcircuitry 38 will continuously compare the results of the detectorcompare register 35 and the detector shift register 14. When thesequence detect circuitry 38 detects a match between its inputs, itsignals a detector hit register 42 to record the value of the detectorcounter 36. This detector hit register 42 value signifies the number ofdetector clock pulses from the start of the emitter sequence to thesensing of a proper detection sequence.

Advanced LiDAR systems will sometimes measure secondary return signals.For example, light rays will typically reflect off a closerobject—otherwise known as the foreground object—and a farther-awayobject—the background object—as a result of the same emitter pulse orseries of pulses. An embodiment of the present invention providesmultiple detector hit registers 42 to account for multiple returnsequences. After the detector counter 36 value for the first returnsequence has been stored, subsequent matches detected by the sequencedetect circuitry 38 will be recorded in the next detector hit register42 in the sequence.

The FIG. 14 blocks represent the circuitry for one emitter and itsmatched detector. For a device with M×N emitters and detectors with alldetectors operating simultaneously, M×N circuits like those representedin FIG. 14 are desired. In devices where K detectors operatesimultaneously, where K is less than M×N, there will be K detectorcircuits desired. Each detector circuit will require mapping circuitrythat maps a detector output to the appropriate detector circuitry forthe current emitter pulse sequence.

In embodiments, the functional blocks in FIG. 14 are implemented indedicated circuitry. One skilled in the art may replace many of thefunctional blocks in FIG. 14 with processes implemented with CPUs,microcontrollers, parallel processors, embedded reduced instruction setcomputing (RISC) machines, programmable logic array, or some other localcomputing circuitry that takes the place of many dedicated circuitblocks.

Referring to FIG. 15 illustrates a timing diagram of elements depictedin the functional blocks of the detector circuitry according to anembodiment. A detector clock 310 frequency is four times the emitterclock 302 frequency. The load pulse generation circuit signal 315initiates the loading of the shift register of pulse generation circuit22 with the bit sequence to be transmitted from the emitter. Incomingbits will be stored in the detector shift register, so this registermust be cleared prior to the detector being enabled. The clear detectorshift register signal 320 sets all of the detector shift register bitsto zero.

The detector counter will serve as the timing sequence throughout thedetection cycle. The counter must be cleared prior to the start of thedetector sequence. The clear detector counter signal 325 sets the all ofthe detector counter bits to zero. The detector hit registers will storethe detector counter values at which the primary and any secondarydetected pulses are sensed. A zero value in these registers signifiesthat a match sequence was not detected, so these registers must becleared prior to the start of the detector sequence. The clear detectorhit register signal 330 sets all of the bits in all of the detector hitregisters to zero.

The output from each emitter 345 is enabled by a logic one appearing atthe output of the pulse generation circuit 22 only when the emitterenable signal 335 is active. The detector enable signal 340 willactivate at the same time as the emitter enable signal 335. The detectorenable signal 340 will activate the detector counter, the detector shiftregister and the sequence detect circuitry.

Upon completion of the shifting of all of the sequence bits out of thepulse generation circuit 22, the emitter enable signal 335 isdeactivated, signifying the end of the emitting portion of theemitter/detector sequence. At the end of the detector sequence thedetector enable signal 340 will be deactivated, which in turn willdiscontinue the incrementing of the detector counter, disable thesequence detect circuitry, and disable any further capturing of data inthe detector hit registers. The control unit will then activate the readdetect hit register signal(s) 355 to process the flight time(s) for thedetected pulse sequence(s).

The timing shown in FIG. 15 utilizes synchronous electronics where allcomponents are driven with a common clock source. One skilled in the artcould produce control circuitry that operates with multiple asynchronousclocks or in a completely asynchronous fashion. The only element thatrequires a clock is the counter unit that will mark the time durationbetween the emitted pulses leaving the emitter and the detected pulsesarriving at the detector circuitry.

Upon completion of the emitter detector sequence and the reading of thedetector hit registers for element m,n, the control unit will computethe time of flight for sequence m,n;

t(flight)_(m,n)=λ_(detector)*(k _(m,n) −K _(m,n))−t _(emitter) −t_(detector)  (eq. 3)

where λ_(detector) is the period of the detector clock

-   -   k_(m,n) is the detector counter value for detector m,n when the        detector match circuitry is triggered for element m,n    -   K is the number of bits in the detector m,n shift register    -   t_(emittor) is the delay from the energizing of the emitter        clock to the energizing of the emitter    -   t_(detector) is the delay from the photons reaching the detector        to the energizing of the circuitry at the input of the detector        shift registers.        The values of t_(emiter) and t_(detector) can be theoretical        values determined from the design of the circuitry or they can        be characterized values based on measurements made with the        manufactured circuitry from known distances.        The distance to the target that provided the reflected return        signal for element m,n is:

$\begin{matrix}{d_{m,n} = \frac{v_{light}*{t({flight})}_{m,n}}{2}} & \left( {{eq}.\mspace{14mu} 4} \right)\end{matrix}$

-   -   where v_(light) is the velocity of light in the medium        (atmosphere, water, oceans, space, etc.) where the device is        used

LiDAR systems will utilize time of flight to determine the distance tothe object that reflected the light. These systems will typically reporta distance at a known angle for every data point. Advanced LiDAR systemswill also report an intensity value for each data point, whereby theintensity value conveys information about the object creating thereflected signal. FIG. 16 illustrates a functional diagram of apreferred embodiment of the present invention where signal intensity iscollected and reported.

Referring to FIG. 16, a functional block used for sending a bit sequenceto an emitter of emitter elements 100 and processing the sensed signalfrom an associated detector of detector elements 200 is depictedaccording to an embodiment. In embodiments, the timer 24 producessynchronized clocks—an emitter clock that controls the timing of thepulses in the pulse generation circuit 22 and a detector clock thatgoverns the processing of information throughout the detectionfunctional blocks. The frequency of the detector clock will typically bean integer multiple of the emitter clock. The integer multiple for thedetector clock will depend on the bit sequence encoding scheme.

The output bit of the pulse generation circuit 22 produces the voltagelevel that will drive the individual emitter. Once the emitter sequencehas started, the detector circuitry begins collecting information fromthe detector of detector elements 200. The sampling circuit 12 producesa multi-bit value that is captured in the intensity shift register 44.Each subsequent transition of the detector clock will capture a newvalue from the sampling circuit 12, with all previous values beingshifted to the right by one location. For sampled values greater thanthe value in the threshold register 30, the threshold compare circuitry32 produces a true value or “1” in a positive logic system. The outputof the threshold compare circuitry 32 is the input value for thedetector shift register 14. A new value is shifted into the detectorshift register 14 on each transition of the detector clock. A detectorcounter 36 is set to zero at the start of the emitter pulse sequence andwill increment its count on each detector clock pulse.

The detector compare register 35 contains the multi-bit value for theemitter pulse sequence. This register is typically a copy of the initialvalue loaded into the pulse generation circuit 22 40. The sequencedetect circuitry 38 will continuously compare the results of thedetector compare register 35 and the detector shift register 14. Whenthe sequence detect circuitry 38 detects a match between its inputs, itsignals the detector hit register 42 to record the value of the detectorcounter 36. This detector hit register 42 value signifies the number ofdetector clock pulses from the start of the emitter sequence to thesensing of a proper detection sequence.

The functional blocks in FIG. 16 support two methods for sequencedetection. The first method is based on the output of the sequencedetect circuitry 38, which compares the binary values generated by thethreshold compare circuitry 32 to the detector compare register 35. Thesecond method ignores the hardware threshold value in the thresholdregister 30 and does not utilize the detector hit register (s) 42. Thissecond method analyzes all of the data in the intensity shift register44 to determine the time at which the first return pulse train wasreceived. This circuitry can utilize noise cancellation techniques toextract secondary pulse times and intensity values for all detectedpulse sequences.

In FIG. 16, a block diagram of circuitry for an emitter element and itsmatched detector is shown according to an embodiment. In embodiments, anoptoelectronic device comprising M×N emitters and detectors with alldetectors operating simultaneously, M×N circuits like those representedin FIG. 16 are desired. In optoelectronic devices where K detectorsoperate simultaneously, where K is less than M×N, there will be Kdetector circuits desired. Each detector circuit will require mappingcircuitry that maps a detector output to the appropriate detectorcircuitry for the current emitter pulse sequence. In embodiments, thefunctional blocks in FIG. 16 can be implemented in dedicated circuitry.In other embodiments, the functional blocks in FIG. 16 with processescan be implemented with CPUs, microcontrollers, parallel processors,embedded reduced instruction set computing (RISC) machines, programmablelogic arrays, or some other local computing circuitry that takes theplace of many dedicated circuit blocks.

FIG. 17 shows detector circuitry wherein each detector utilizes amicroprocessor unit (MPU) to determine the times at which reflectedsignals are received and the associated intensities of the reflectedsignals. FIG. 17 depicts detector circuitry for an M×N array ofdetectors, where individual detectors are denoted as m, n where m variesfrom 0 to M−1 and n varies from 0 to N−1. The number of detectors can beequal to the number of emitters, or can be many times greater than thenumber of emitters.

The input signal from each detector is digitized by an A/D converter 12and the digitized signal is presented to the intensity shift register44. Every intensity shift register 44 captures a new multi-bit intensityvalue on the leading edge of the detector clock. Values are shifted intothe intensity shift registers 44 throughout the entire detection cycle.At the end of the detection cycle each MPU will begin processing thecaptured and presented information to determine the clock sequences atwhich valid reflected signals were received. All activated intensityshift registers 44 are clocked for the same number of clock cyclesthroughout the detection cycle.

The timer 24 will control the clocking of data into all of the intensityshift registers 44. Each element in the detector shift registers is amulti-bit value, and the number of required elements in each intensityshift register will depend on the range of the device, the desiredaccuracy of the distance measurements, the number of bits in eachemitter sequence, and the rate multiplier of the detector clock to theemitter clock. The number of elements for each detector shift registerelements is:

# of detector shift register elements>E*L+(2*R*f _(emitter) *L)/v_(light)  (eq. 5)

where E is the number bits in each emitter shift register

-   -   L is the clock multiplier signifying L detector clock pulses for        each emitter clock pulse    -   R is the specified range of the device, signifying the maximum        distance that can be measured    -   f_(emitter) is the frequency of the emitter clock    -   v_(light) is the velocity of light in the medium (atmosphere,        water, oceans, space, etc.) where the device is used

The circuitry blocks for MPU m,n 450 are shown in FIG. 17. The intensityshift registers 44 are addressable and readable over the intensity shiftregister bus 452 by the controller 20 and by each MPU. Upon thecompletion of the detection cycle, MPU m, n 450 reads the value fromintensity shift register m, n 454 and the value from the detectorcompare register m, n 456. For algorithms that utilize only singledetector information, these two lone data elements are used by the MPUto process the received waveform and determine how many return signalswere detected and the associated intensity for each return signal. Thenumber of elapsed clock pulses for each detected signal is stored by MPUm, n 450 in the detector hit registers m, n 458, and their associatedintensities are stored in the intensity registers m, n 460.

Many algorithms for signal analysis and detection utilize informationfrom neighboring detectors and/or emitters. The detector bus 452 allowseach MPU to access captured return signals from neighboring detectors.In addition, each MPU can access the detector compare register 456 forevery detector via the detector bus to determine if an on-coincidentaxis emitter was activated for that detector during the previous emittersequence. A null value in a neighboring detector compare register 456will signify to other MPUs that an on-coincident axis emitter was notactive during the previous emitter cycle.

FIG. 17 shows two other MPUs in the detector circuitry—MPU 0,0 462 andMPU M−1,N−1 464. For a device that has M×N detectors, there will be M×NMPUs, with each MPU having its own dedicated detector hit registers andintensity registers, and having access to all intensity shift registersand all detector compare registers via the detector bus.

The device MPUs are dedicated microcontroller units that have reducedinstruction sets specifically tailored to signal processing. Each MPUcontains a dedicated ALU (arithmetic logic unit), control store,processing registers, instruction memory, and configuration memory. Uponpower up of the device, each MPU is configured to establish itsassociated on-coincident axis emitter. According to an embodiment, notevery MPU will be associated with an on-coincident axis emitter.

High-speed applications require one MPU for each detector. One skilledin the art will understand that conventional multiplexing techniques canbe applied to devise a system wherein one MPU could service multipledetectors. The functionality of all of the MPUs could be replaced by acontroller 20 with sufficient resources.

Referring to FIG. 18a , a grid 365 showing an ideal location 370 foremitted beams is depicted according to an embodiment. Such a grid couldbe used for device characterization, whereby the transmission vector ofeach emitter is determined and stored in the vector memory. Prior tocharacterization, micro lenses can be modified for more precise aiming.A misaligned emitter beam 360 misses the ideal location 370 on the grid365 in both the horizontal and vertical dimensions. FIG. 18b depicts anexpanded view of a beam aligned on grid 365 and a misaligned emitterbeam 360. The horizontal offset 375 is reduced by making changes to thevoltages to the horizontal lens control for the lens that corresponds tothis emitter. The vertical offset 380 is reduced by making changes tothe vertical lens control for the lens that corresponds to this emitter.The voltages used to align each micro lens are stored in the vectormemory. These voltage values are saved during power down of the device.During the power up sequence, the control unit will load the values forthe micro lenses into the lens control circuitry for each micro lens.

The grid 365 shown in FIG. 18a can also be used for devicecharacterization. For each emitter, the as-built emitter vector(coincident axis) must be determined. In embodiments, characterizationincludes measuring the point at which each emitter beam contacts thegrid 365 and determining the vector of the beam, where the beam vectoris described relative to a known vector on the device. A typical way ofexpressing the emitter vector is to utilize uvw vector nomenclaturewhere the vector is relative to the normal vector of the device. Thecharacterized vector for each emitter is stored in the vector memory andsaved when the device is powered off.

Referring to FIG. 19 a dense detector array 290 according to anembodiment is depicted. In embodiments, dense detector array 290comprises a plurality of detector elements for each emitter element. Thedense detector array 290 can be utilized with waveguide detectors orwith macro lens detectors. When used with macro lens detectors, thedetector characterization is performed after the macro lens ispermanently attached to the device, thus accounting for any alignmenttolerances between the dense detector array 290 and the lens.Characterization of dense detector array 290 can be used to determinewhich detector element has the greatest signal strength for each emitterelement. In FIG. 19, primary detector 292 has been established as thebest on-coincident axis match for an emitter. Characterizationinformation for detectors can be saved in vector memory.

In embodiments, detector elements in a first concentric ring surroundinga primary detector 292 are designated as secondary detectors 294. Insome embodiments, secondary detectors 294 are adjacent neighboringdetectors that form the first concentric ring. Each primary detector 292in FIG. 19 can comprise three or more secondary detectors 294. Thesecondary detectors can be utilized to sample data to enhance the signalstrength of the primary waveform. In embodiments, sampled waveforms fromthe secondary detectors can be utilized in a post-processed mode toperform noise suppression and/or noise cancellation on the primarywaveform. Detectors in the second concentric ring surrounding theprimary detector 292 can be designated as a tertiary detector 296.

In embodiments, each primary detector 292 in FIG. 19 can comprise threeor more tertiary detectors 296. The tertiary detectors can be utilizedto sample data to enhance the signal strength of the primary waveform.In other embodiments, sampled waveforms from the tertiary detectors canbe utilized in a post-processed mode to perform noise suppression and/ornoise cancellation on the primary waveform. In addition to noisesuppression and noise cancellation, the primary, secondary and in somecases tertiary detector information can be utilized to perform one ormore of the following techniques including but not limited to timedomain methods like FFT, DFT and largest common point, statisticalmethods like least squares, gradient following, projection kernels andBayesian, and pattern matching techniques like Boyer-Moore,Kuth-Morris-Pratt, finite state neural networks and Graham's. Inoperation, for example, the optical center of the inbound signal may notcoincide precisely with the center of a detector. For each emitter,floating point values can be used to designate a primary detector. Byexpressing the row and column of the primary detector as floating pointnumbers, the neighboring detectors can be weighted accordingly whenmultiple detectors are used to receive incoming sampled waveforms.

FIG. 20 portrays an orthogonal detector layout for a dense array in apreferred embodiment. A detector designated as a primary detector 292 isshown near four secondary detectors 294 and four tertiary detectors 296.

Referring to FIG. 21, a functional flowchart for the operation of theoptoelectronic device according to an embodiment is shown. Upon power upat 400, the control unit 20 will determine the type of device 240. Whenthe device 240 has micro lens emitters, the control unit 20 at 404 willread the lens voltages from vector memory and store the appropriatevalues in the lens control circuitry foe each micro lens. Circuitry usedfor transmission and receipt of light are cleared, including samplingcircuit 12 at 406 and detector shift registers 14 at 408. Theseoperations are performed on emitter elements 100 and detector elements200 on the device 240.

When the device 240 is enabled at 410, the control unit 20 determinesthe pulse patterns for each emitter of emitter elements 100 and willload shift registers of the pulse generation circuit 22 at 412, cleardetector counters at 414 and enable emitter elements 100 and detectorelements 200 at 416 that will be utilized in the ensuingemitter/detector sequence. At the completion of the detector sequence at418, the resultant values are retrieved for each detector of detectorelements 200 that was activated for the sequence. At 420, for devicesthat utilize hardware matches, the detector hit register 4 and intensityregisters are read for each enabled detector. For devices that utilizesoftware matches the intensity shift registers are read for eachprimary, secondary and tertiary shift register at 426.

Having collected the appropriate information for all enabled detectors,the control unit will compute flight times at 428, write the vectors at430 to image memory, write a distance at 432 to image memory, and writethe time stamp at 434 to image memory that marks the beginning of theemitter transmission for each emitter of emitter elements 100. Uponcompletion of the computations and storage for all detectors, thecontents of image memory are transmitted via the I/O interface at 436 tothe upstream control unit 20.

FIG. 22 depicts the use of a group of LiDAR units in accordance with oneembodiment of the present invention. A passenger vehicle 470 has along-range device 472 used for real-time mapping and forward obstacleidentification. Two shorter-range, wider-field-of-view front-facingdevices 474 are used for mapping of adjacent lanes, road edges, andconnector roadways in addition to the identification of obstacles notaligned with the direction of travel. Each side of the vehicle 470 hastwo wide-angle devices 476 used for object identification and velocitydetermination of neighboring vehicles. Two outboard rear-facing devices478 are used for blind spot detection in human-operated vehicles or forobject identification in autonomous vehicles. A rear-facing device 480is used for object identification and velocity determination ofapproaching vehicles. All of the devices 472, 474, 476, 478, 480 can beidentical devices with a single field of view, or they can beapplication specific, each with a separate field of view,emitter/detector wavelength, detection and measurement distanceoperating range, and number of emitters.

FIG. 23 depicts the use of a group of LiDAR units in accordance withanother embodiment of the present invention. A data acquisition aircraft484 utilizes a single wide-field-of-view device 486 for terrain 496mapping, pixel depth acquisition, or remote sensing. Alternately, theaircraft 484 implements a higher-resolution, wider-field-of-viewapparatus 488 that utilizes multiple devices 492. The exploded view 490of the apparatus 488 depicts devices 492 oriented in a geodesic patternso the combined fields-of-view 494 for all devices 492 yields ahigher-resolution acquisition path than could be realized with a singledevice 492.

In various embodiments of the present invention the emitters areconstructed using 650 nanometer lasers. One skilled in the art canutilize other wavelengths for emitter and detector construction as longas the emitted radiation maintains its directionality while transmittingthough the medium and as long as the selected wavelength is not highlyabsorptive by the objects contained in the medium. In some embodiments,the light energy is emitted and received as collimated or coherentelectromagnetic energy, such as common laser wavelengths of 650 nm, 905nm or 1550 nm. In some embodiments, the light energy can be in thewavelength ranges of ultraviolet (UV)—100-400 nm, visible—400-700 nm,near infrared (NIR)—700-1400 nm, infrared (IR)—1400-8000 nm,long-wavelength IR (LWIR)—8 um-15 um, or far IR (FIR)—15 um-1000 um. Thevarious embodiments of the present invention can provide reduction ofinterference at these various wavelengths not only among emitted andreflected light energy of LiDAR devices, but also emitted and reflectedlight energy from other ambient sources such as vehicle headlights andthe sun that will also be sources of interference for typical LiDARunits.

Various embodiments of devices and methods have been described herein.These embodiments are given only by way of example and are not intendedto limit the scope of the invention. It should be appreciated, moreover,that the various features of the embodiments that have been describedmay be combined in various ways to produce numerous additionalembodiments. Moreover, while various materials, dimensions, shapes,configurations and locations, etc. have been described for use withdisclosed embodiments, others besides those disclosed may be utilizedwithout exceeding the scope of the invention.

Persons of ordinary skill in the relevant arts will recognize that theinvention may comprise fewer features than illustrated in any individualembodiment described above. The embodiments described herein are notmeant to be an exhaustive presentation of the ways in which the variousfeatures of the invention may be combined. Accordingly, the embodimentsare not mutually exclusive combinations of features; rather, theinvention can comprise a combination of different individual featuresselected from different individual embodiments, as understood by personsof ordinary skill in the art. Moreover, elements described with respectto one embodiment can be implemented in other embodiments even when notdescribed in such embodiments unless otherwise noted. Although adependent claim may refer in the claims to a specific combination withone or more other claims, other embodiments can also include acombination of the dependent claim with the subject matter of each otherdependent claim or a combination of one or more features with otherdependent or independent claims. Such combinations are proposed hereinunless it is stated that a specific combination is not intended.Furthermore, it is intended also to include features of a claim in anyother independent claim even if this claim is not directly madedependent to the independent claim.

Any incorporation by reference of documents above is limited such thatno subject matter is incorporated that is contrary to the explicitdisclosure herein. Any incorporation by reference of documents above isfurther limited such that no claims included in the documents areincorporated by reference herein. Any incorporation by reference ofdocuments above is yet further limited such that any definitionsprovided in the documents are not incorporated by reference hereinunless expressly included herein.

For purposes of interpreting the claims for the present invention, it isexpressly intended that the provisions of Section 112, sixth paragraphof 35 U.S.C. are not to be invoked unless the specific terms “means for”or “step for” are recited in a claim.

1-37. (canceled)
 38. An array-based light detection and ranging (LiDAR)unit comprising: a non-scanning, solid-state device having a multitudeof emitter/detector sets arranged on a generally planer surface toestablish a unique on-coincident axis associated with eachemitter/detector set in an array of emitter/detector sets configured tocover a macro field of view for the unit, each emitter/detector setconfigured to emit and receive light energy on a specific coincidentaxis unique for a micro field of view of at least the detector of thatemitter/detector set via a unique corresponding micro-lens element of amicro-lens array; and a control system coupled to the array ofemitter/detector sets to control initiation of light energy from eachemitter and to process time of flight information for light energyreceived on the coincident axis by the corresponding detector for theemitter/detector set, wherein time of flight information for lightenergy corresponding to the array of emitter/detector sets providesimaging information corresponding to the field of view for the unit andinterference among light energy corresponding to an emitter of thespecific coincident axis of an emitter/detector set is reduced withrespect to detectors in the LiDAR unit other than the detector of theemitter/detector set corresponding to the specific coincident axis. 39.The array-based LiDAR unit of claim 38, wherein a number ofemitter/detector sets ranges from a 16×16 array of emitter/detector setsto an array of 4096×4096 emitter/detector sets.
 40. The array-basedLiDAR unit of claim 38, wherein each emitter/detector set is a singlepair of an emitter and a detector.
 41. The array-based LiDAR unit ofclaim 38, wherein a single emitter is optically configured to provideon-coincident axis light energy to multiple different detectors, witheach unique on-coincident axis combination of the single emitter and onemicro-lens for that emitter and a plurality of different detectors eachassociated with a different detector micro-lens, each common emitter andunique detector comprising a different emitter/detector set.
 42. Thearray-based LiDAR unit of claim 38, wherein the light energy is emittedand received as collimated electromagnetic energy selected from thewavelength ranges of: ultraviolet (UV)—100-400 nm, visible—400-700 nm,near infrared (NIR)—700-1400 nm, infrared (IR)—1400-8000 nm,long-wavelength IR (LWIR)—8 um-15 um, or far IR (FIR)—15 um-1000 um. 43.An array-based light detection and ranging (LiDAR) unit comprising: anon-scanning, solid-state device having a multitude of emitter/detectorsets arranged on a generally planer surface to establish a uniqueon-coincident axis associated with each emitter/detector set in an arrayof emitter/detector sets configured to cover a macro field of view forthe unit, each emitter/detector set configured to emit and receive lightenergy on a specific coincident axis unique for a micro field of viewfor at least the detector of that emitter/detector set; a global lensingarrangement that is optically coupled between the macro field of viewand the array of emitter detector sets and is selectively adjustablewith respect to light energy emitted and received by the unit; and acontrol system coupled to the array of emitter/detector sets to controlinitiation of light energy from each emitter and to process time offlight information for light energy received on the coincident axis bythe corresponding detector for the emitter/detector set, wherein time offlight information for light energy corresponding to the array ofemitter/detector sets provides imaging information corresponding to thefield of view for the unit and interference among light energycorresponding to an emitter of the specific coincident axis of anemitter/detector set is reduced with respect to detectors in the LiDARunit other than the detector of the emitter/detector set correspondingto the specific coincident axis.
 44. The array-based LiDAR unit of claim43, wherein a number of emitter/detector sets ranges from a 16×16 arrayof emitter/detector sets to an array of 4096×4096 emitter/detector sets.45. The array-based LiDAR unit of claim 43, wherein eachemitter/detector set is a single pair of an emitter and a detector. 46.The array-based LiDAR unit of claim 43, wherein a single emitter isoptically configured to provide on-coincident axis light energy tomultiple different detectors, with each unique on-coincident axiscombination of the single emitter and one micro-lens for that emitterand a plurality of different detectors each associated with a differentdetector micro-lens, each common emitter and unique detector comprisinga different emitter/detector set.
 47. The array-based LiDAR unit ofclaim 43, wherein the light energy is emitted and received as collimatedelectromagnetic energy selected from the wavelength ranges of:ultraviolet (UV)—100-400 nm, visible—400-700 nm, near infrared(NIR)—700-1400 nm, infrared (IR)—1400-8000 nm, long-wavelength IR(LWIR)—8 um-15 um, or far IR (FIR)—15 um-1000 um.
 48. An array-basedlight detection and ranging (LiDAR) unit comprising: a non-scanning,solid-state device having a multitude of emitter/detector sets arrangedon a generally planer surface to establish a unique on-coincident axisassociated with each emitter/detector set in an array ofemitter/detector sets configured to cover a macro field of view for theunit, each emitter/detector set configured to emit and receive lightenergy on a specific on-coincident axis via an optical waveguide thatprovides a unique micro field of view for at least the detector of thatemitter/detector set; and a control system coupled to the array ofemitter/detector sets to control initiation of light energy from eachemitter and to process time of flight information for light energyreceived on the coincident axis by the corresponding detector for theemitter/detector set, wherein time of flight information for lightenergy corresponding to the array of emitter/detector sets providesimaging information corresponding to the field of view for the unit andinterference among light energy corresponding to an emitter of thespecific coincident axis of an emitter/detector set is reduced withrespect to detectors in the LiDAR unit other than the detector of theemitter/detector set corresponding to the specific coincident axis. 49.The array-based LiDAR unit of claim 48, wherein a number ofemitter/detector sets ranges from a 16×16 array of emitter/detector setsto an array of 4096×4096 emitter/detector sets.
 50. The array-basedLiDAR unit of claim 48, wherein each emitter/detector set is a singlepair of an emitter and a detector.
 51. The array-based LiDAR unit ofclaim 48, wherein a single emitter is optically configured to provideon-coincident axis light energy to multiple different detectors, witheach unique on-coincident axis combination of the single emitter and onemicro-lens for that emitter and a plurality of different detectors eachassociated with a different detector micro-lens, each common emitter andunique detector comprising a different emitter/detector set.
 52. Thearray-based LiDAR unit of claim 48, wherein the light energy is emittedand received as collimated electromagnetic energy selected from thewavelength ranges of: ultraviolet (UV)—100-400 nm, visible—400-700 nm,near infrared (NIR)—700-1400 nm, infrared (IR)—1400-8000 nm,long-wavelength IR (LWIR)—8 um-15 um, or far IR (FIR)—15 um-1000 um.